This invention relates to a steering wheel installed in a vehicle such as an automobile and more particularly to a steering wheel equipped with a relay component comprising slip rings and contact pins.
There is a known steering wheel equipped with a relay component and more specifically an early publication of Japanese Patent Application (OPI) No. 95232/82 discloses a steering wheel with a pad of unrotatable type.
In a steering wheel so arranged as shown in FIGS. 1 and 2, a pad side sun gear 53a and a column side sun gear 53b are respectively installed in the upper and lower portions or the outer periphery of a boss 52 fixed to the upper end of a steering shaft 51, both sun gears 53a, 53b being concentric with the steering shaft 51.
A pad side planet gear 55a and a column side planet gear 55b are assembled to a boss plate 54 extending outwardly from the outer periphery of the center of the boss 52 in between the sun gears 53a, 53b. The planetary gears 55a and 55b are engaged with the sun gears 53a, 53b while rotating on their own axes and moving around the sun gears 53a, 53b, respectively. A planet gear mechanism is thus constructed.
Various kinds of electronic equipment 60 such as a control switch are installed on the pad 56 of the steering wheel and a relay component for supplying power to the electronic equipment is incorporated in the planet gear mechanism.
The relay component is normally installed on the under surface of the pad side sun gear 53a and comprises a pad side slip ring 57a having its surface coated with grease G as a lubricant, a plurality of pad side contact pins 58a, each being fixed to the boss plate 54 through a contact pin holder 59 in such a manner as to contact the surface of the slip ring 57a, column side slip ring 57b installed on top of the column side sun gear 53b and having its surface coated with grease G, and a plurality of pad side contact pins 58b, each being fixed to the boss plate 54 through the contact pin holder 59 in such a manner as to contact the surface of the slip ring 57b.
As shown in FIG. 2, the contact pin holder 59 includes two subdivided pieces 59c and 59d constituting a cylindrical body having a discoidal top cover 59a and a discoidal bottom cover 59b, a through-hole 61 being in the centers of both covers 59a and 59b.
Ends of each of the contact pins 58a, 58b serve as contact pieces 64a, 64b in contact with the slip rings 57a. 57b. The end portions 64a, 64b pass through the holes 61 formed in the top cover 59a and the bottom cover 59b and extend outwardly therefrom.
Both ends of a spring 62 are respectively fitted to the base portions of the contact pins 58a, 58b, the contact pins 58a, 58b being biased by the spring 62 in the direction opposite to each other.
In the steering wheel thus constructed, the pad side and column side slip rings 57a, 57b and the pad side and column side contact pins 58a, 58b are caused to keep sliding contacts through the steering operation and thus the pad and column sides are in electrical conduction.
Two pairs of contact pins 58a, 58b arranged electrically in parallel can be used in order to improve reliability.
In the steering wheel thus constructed, the relay component including, in combination, the pad side contact pin 58a, the pad side contact pin 58b, the contact pin holder 59 and the spring 62 has provided the following problems:
That is, during steering operation in FIG. 1, upon rotation of the steering ring 63, the boss plate 54 is rotated, so that the pad side contact pin 58a and the column side contact pin 58b are rotated about the shaft 51 in sliding contact with the pad side slip ring 57a and the column side slip ring 57b, those rings being kept unrotatable. In this case, the inclinations of the two contact pins 58a, 58b change as if the front ends thereof were dragged each time the direction of rotation changes, and this causes the front ends thereof to catch the slip rings 57a , 57b and thus the contact pins 58a, 58b to rattle.
The above rattling provides generation of unusual sounds and causes the defective connection between the two contact pins 58a, 58b and the spring 62.
Further, since the contact pins 58a, 58b each are kept in contact with the slip rings 57a, 57b as set forth above, the contact pins 58a, 58b always pass on the same loci of sliding revolutions on the slip rings 57a 57b, respectively. In consequence, only the contacting faces of them will wear out if they are repeatedly used and their durability has posed a problem. This problem becomes conspicuous when two pairs of contact pins 58a, 58b are installed. Another problem is that, when grease G is applied to the surfaces of the slip rings 57a, 57b, the grease G applied onto the loci may be scraped off or driven to both edge portions by the contact pins 58a, 58b and the surfaces of the slip rings 57a 57b on the loci may be exposed.
Accordingly, unusual sounds originated in the direct contacts of the slip rings 57a 57b with the contact pins 58a, 58b give the driver an unpleasant feeling during the steering operation. Moreover, the contact pins 58a, 58b are unable to slide smoothly, and contact pins 58a, 58b and the slip rings 57a 57b quickly wear out.